fix: remove hold WaitGroup in TestConcurrentFetch

[spikecurtis]

Fixes: coder/internal#950

Pretty sure the intention of the hold wait group is to try to get the two goroutines that the test starts running at the same time. But, that should be the case for two goroutines started anyway.

The use of hold doesn't actually guarantee concurrent execution of Acquire, just that both goroutines get as far as Done() --- the go scheduler could run them serially without incident.

So I've chosen to just remove the use of hold to simplify.

But, for posterity, the data race was due to incrementing by 1 in the loop along with the goroutine that calls Done. You could increment by 1 and then back down to 0 before the second iteration of the loop starts. This then causes a data race with calling Wait() in the first goroutine and Add() in the second iteration. c.f. https://pkg.go.dev/sync#WaitGroup.Add

[spikecurtis]

• fix: remove hold WaitGroup in TestConcurrentFetch #19617 👈 (View in Graphite)
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[aslilac]

thanks for waiting for me to get back from vacation for the review 😄